Field emission devices are known in the art. Such devices typically employ electron emitters in concert with applied electric fields to induce electron emission by quantum mechanical tunnelling through the potential barrier at the surface of the emitters. Electron emission is exponentially dependant on the electric field strength at the emission site and emission is increased by reducing the potential barrier width by increasing the applied electric field strength.
Further, non-related photon-induced electron emission is known in the art and is commonly referred to as the photoelectric effect. Photon-induced electron emission from surfaces requires that the exciting photons must possess at least a minimum energy to induce an electron to escape from the surface of the material in which it resides. For materials of interest, this "excitation energy" is between 2-5 electron volts. As such, longer wavelength photons do not possess sufficient energy to induce electron emission. This lower energy limit may be referred to as the photoelectric emission threshold. This limitation precludes the use of infra-red or longer wavelength photon sources to induce electron emission or, conversely, infra-red or longer wavelength photon detectors are not practically employed by methods of the prior art.
Accordingly, there exists a need for devices which provide increased electron emission without the very high electric fields of prior art devices; and there exists a need for devices which provide low-energy photon-induced electron emission not available with the devices of the prior art.